Brown Aromatics and Beef: In a large skillet over medium-high heat, combine the ground beef, minced garlic, diced bell pepper, and approximately two-thirds of your diced 1/2 medium onion (having reserved the final one-third for topping). Cook, breaking up the beef with a spoon, until the beef is thoroughly browned. Drain off any excess fat from the skillet.
Build Chili Flavor: To the skillet with the browned beef mixture, add the chili powder, smoked paprika, cumin, black pepper, salt, sugar substitute, Worcestershire sauce, no-sugar-added tomato sauce, tomato paste, and water. Stir well to ensure all ingredients are fully combined.
Simmer Chili: Bring the chili mixture to a gentle simmer. Reduce the heat to low, cover the skillet, and let it simmer for at least 20-25 minutes, allowing the flavors to meld. Stir occasionally.
Refine Chili Texture (Highly Recommended): For an authentic "hot dog chili" texture, carefully transfer the simmered chili to a food processor or use an immersion blender directly in the skillet (if heat-safe and contents are not too shallow). Process or blend until the beef is broken down into very fine pieces. Be cautious when blending hot liquids.
Prepare Hot Dogs & Assemble: Preheat your oven to 375-400°F (190-200°C). Slice the 4 beef hot dogs lengthwise down the middle, and then cut each resulting piece in half (or slice into rounds if preferred). Arrange the hot dog pieces in a single layer covering the bottom of your small oven-safe casserole dish.
Layer and Top: Pour the prepared chili evenly over the hot dogs in the casserole dish. Sprinkle the 1/2 cup of shredded cheddar cheese over the chili. Finally, distribute the reserved one-third of diced onion (from step 1) over the cheese.
Bake Casserole: Place the casserole dish in the preheated oven. Bake for 15-20 minutes, or until the casserole is hot throughout, the chili is bubbly, and the cheese is melted and lightly golden.
Serve and Enjoy: Carefully remove the casserole from the oven. Let it rest for a few minutes before serving. If using, garnish individual servings with additional fresh diced onion.